Wall chasing

Wall chasing is cutting channels in walls and screed for concealed electrical wiring, low-voltage cables and pipes. Thanks to chases, wires and pipes do not stick out and the walls remain flat for finishing. But a chase always weakens the structure, so it must be made only according to a plan and in permitted places.

What is used. Professionally, a chasing machine (wall chaser) with an industrial vacuum connected. An unguarded angle grinder works dry and raises a cloud of concrete dust, which is harmful for people and neighbours in a residential building, and the depth is also hard to control. A hammer drill with a chisel leaves ragged edges and cracks. For brick and aerated concrete lighter tools are acceptable; concrete needs a diamond blade.

How to do it properly. Cable routes run strictly vertically and horizontally, parallel to the walls. Diagonal chases are not made: no one will find the cable later when drilling. The chase size is chosen for the cable or pipe and the plaster layer: extra width and depth weaken the wall. The chase is closed after the route has been checked and photographed, because after plastering the cable is hard to find.

The main restriction. In load-bearing reinforced-concrete walls, pylons and slabs, horizontal chases are not acceptable: according to popular sources, reinforcement often lies at a depth of about 30–35 mm, and a deep horizontal chase will cut it and the protective cover. In multi-storey buildings, chasing load-bearing walls is best avoided altogether without agreement from the designer and the management company. That is why in monolithic buildings routes run through the floor screed and across the ceiling behind plasterboard or a stretch ceiling, and drop vertically to sockets and switches where that is permitted.

How to avoid chasing. If the wall is load-bearing or you do not want to weaken it, a false wall or plasterboard box, cable-channel skirting, routing through the ceiling and floor, and building channels in during masonry of partitions are used. In block and brick partitions chasing is easier, but still according to the plan. A separate point is the hole for a socket box: it is drilled with a core bit, not hacked out.

Typical mistakes: chasing "as you go" without a plan; making diagonal and too deep chases; chasing load-bearing walls and cutting reinforcement; laying cables without conduit where it is needed; not photographing the routes; forgetting the separation between power and low-voltage lines. Our working project includes an electrical plan and a lighting plan with a control scheme, so the contractor knows where and which lines run. And later you can find the routes from the drawings and photos: a year from now you should know where you can drill.